1. Field of the Invention
This invention relates generally to anti-fouling coatings, and more particularly to an anti-fouling coating containing capsaicin as an active ingredient.
2. Brief Description of the Prior Art
Various antifungal, algeacides, and antifouling agents have been used in coatings and paints for different environments to prevent mildew, fungus, and sea water flora and fauna.
The mildew or fungus which grows on house paints and the like, utilizes the paint medium, or in some cases, the underlying substrate, such as wood, as the nutrient. The micelia and fruiting bodies of the fungi contact or penetrate the paint film and thus, through intimate contact with any fungicides in the film (to a large extent regardless of whether the fungicides are highly soluble, slightly soluble, or insoluble in water), the fungi are destroyed.
In cooling towers and piping systems utilizing fresh water, slime and algea may develop if effective compounds for combating their growth are not present. In the area of anti-fouling paints, a relatively narrow group of compounds is useful for preventing the fouling of marine structures, such as boat or ship hulls, pilings, oil well drilling towers, and the like, by organisms common in sea water and brackish water. Such organisms include; algea, slime, hydroids, mollusks, barnacles, and the like.
A critical factor, particularly in fresh water and sea water marine applications is that the active ingredient in the coating or paint cannot be highly soluble or it will leach out of the anti-fouling coating or paint in a short period of time and drastically reduce its effectiveness. On the other hand, many anti-fouling coatings and paints provide an active ingredient which is allowed to leach over a period of time or which forms a film on the exterior of the coated or painted surface to combat the fouling organisms.
Conventional anti-fouling agents used in marine anti-fouling coatings and paints include inorganic heavy-metal compounds such as mercury and copper, and various types of organic and organo-metallic compounds. However, the inorganic metal compounds loose their effectiveness rapidly in sea water contaminated with hydrogen sulfide. Some of the organic anti-fouling agents are effective for preventing the attachment of only particular marine lives, but are not effective against others. Among the inorganic and organic compounds, there are many which may be effective for preventing the attachment of marine lives, but are not suited for practical use because of their toxicity to the human body or other marine life, or will pollute the environment.
Takagi et al, U.S. Pat. No. 3,912,519 discloses an anti-fouling ship bottom paint containing an active ingredient comprising 5-chloro-4-phenyl-1,2-dithiol-3-one or a mixture of that compound and 3,5-di-lower alkyl-4-hydroxy-benzylidene. These compounds have such a high rate of decomposition that they have no residual toxicity and cause no environmental pollution.
Davie, U.S. Pat. No. 3,997,461 discloses an anti-foulant coating composition composed of two components (A) and (B) which are mixed immediately before the composition is applied. The active ingredient of Component A is a base of coal-tar pitch or equivalent and epoxy resin. The active ingredients of component B are a curing agent for the epoxy resin and a solid organo tin toxicant, mainly a solid trialkylin carboxylate. The toxicant may either be a slurry of needle-like crystals or the toxicant may be dissolved in a solvent. The toxic activity is due to the tin content of the organatin toxicant.
Milne et al, U.S. Pat. No. 4,021,392 discloses an anti-fouling marine paint composition which releases organo tin ions into sea water. The composition comprises; a film-forming copolymer of at least one triorgano tin salt of an olefinically unsaturated carboxylic acid and the balance of the copolymer being units of at least one olefinically unsaturated comonomer, a substantially water insoluble metalliferous pigment capable of reacting with sea water to form the mater soluble metal compound, and a hydrophobic organic retarder for retarding the rate of ion exchange between sea water and the copolymer.
Dupont, U.S. Pat. No. 4,127,687 discloses an anti-fouling marine paint containing an organic binder and an effective amount of certain 3-isothaizolones.
Freeman et al, U.S. Pat. Nos. 4,789,567 and 4,968,538 disclose an abrasion resistant coating and method of application wherein a protective coating of resin containing finely divided abrasion resistant particles is diluted with a solvent and applied to a surface. The applied coating is cured to achieve either a single layer of inert material dispersed in the resin, or two layers including a dense layer of inert material in resin covered by a thin layer of resin, and to provide a glossy or matte appearance as desired.
"Capsaicin" is an incredibly powerful and stable alkaloid seemingly unaffected by heat or cold, which retains its original potency over time, cooking, or freezing. Capsaicin is the bitter compound and naturally occurring heat source for chile peppers of the genus Capsicum, as C. frutescens, and is concentrated mostly in the placental tissue of the pepper. For every hundred parts of capsaicin in the placental tissue, there are six parts in the rest of the fruit tissue, and four parts in the seeds. Two very pungent synthetic capsainoid compounds are capsaicin (C) and dihydrocapsaicin (DHC).
The technique for determining capsaicin pungency is by high-pressure liquid chromatography (HPLC). The standard industry measurement for capsaicin levels is given in Scoville Heat Units. Pure capsaicin equals 16 million Scoville Units. The following chart illustrates the range of Scoville Heat Units present in various chile pepper varieties utilizing HPLC.
______________________________________ Chile Pepper Variety Approx. Scoville Units ______________________________________ Habenaro, Bahamian 100,000-300,000 Santaka, Chiltepin, Thai 50,000-100,000 Aji, Rocoto, Piquin, Cayenne, Tabasco 30,000-50,000 de Arbol 15,000-30,000 Yellow Wax Hot, Serrano 5,000-15,000 Jalapeno, Mirasol 2,500-5,000 Sandia, Cascabel 1,500-2,500 Ancho, Pasilla, Espanola 1,000-1,500 NuMex Big Jim, NM 6-4 500-1,000 R-Naky, Mexi-Bell, Cherry 100-500 Mild Bells, Pimiento, Sweet Banana 0 ______________________________________
Various kinds of pepper derivatives have been known to be used to repel pests.
Yaralian, U.S. Pat. No. 4,455,304 discloses a composition for repelling birds wherein the active ingredients are finely divided dried cayenne pepper (30,000-50,000 Scoville Units), finely divided dried garlic diluted by inert, finely divided mineral material (dry application) or water (liquid application) for application to the earth surface or to growing plants. The garlic constituent is present in at least about one-fifth to about five times the pepper constituent.
Oleoresin Capsicum is an extract of natural spice and is commonly used in foods and medicinal applications whenever a warming or pungent sensation is desired.
Kalsec, Inc. of Kalamazoo, Mich. produces a commercially available oleoresin capsicum product which is commonly used as a food flavoring under the product name of "Oleoresin Capsicum, African type, 6% MC". This product is made from the dried fruit of Capsicum frutescens mixed with vegetable oils and contains 5.40% to 6.60% capsainoids.
Fischer, U.S. Pat. No. 5,226,380 discloses a marine coating containing cayenne pepper and method of applying the coating. Fischer teaches applying a layer of waterproof adhesive or paint to the surface to be protected, and then applying a deposit of cayenne pepper (30,000-50,000 Scoville Units), to the adhesive layer while it is in the uncured state. A layer of copper granules may also be applied to the adhesive layer after the cayenne pepper in sufficient density to cover the entire surface while leaving sufficient spacing between the copper granules to form a permeable layer through which the repellent properties of the pepper can diffuse and in cooperation with the copper granules provide additional protection for the surface. Alternatively, a copper wire screen, an unwoven mat of copper wires, or short chopped lengths of copper wire, may be used instead of the granules to provide a permeable layer of copper. Fischer also teaches that at least part of the anti-fouling materials may be mixed with the adhesive and applied simultaneously. As the paint leaches away, the anti-foulant is exposed to "release heat" to repel marine organisms in the vicinity of the surface.
In the Fischer process the anti-foulant properties of the pepper particles would be short lived whether it is applied as an outer layer or mixed with the paint prior to application, due to leaching either into the paint mixture or into the water surrounding the coating. Fischer also utilizes particles or an oleoresin capsicum derived from the cayenne pepper which would have a pungency rating of only 30,000-50,000 Scoville Units. It has also been found that merely mixing an oleoresin with an adhesive, ablative paint, or epoxy or polyurethane compounds, will often adversely affect the curing time and physical properties of the coating material.
The present invention is a significant improvement in that it utilizes an oleoresin capsicum, capaiscin particles, or capsaicin crystals which are derived from the Habenaro pepper which has a pungency rating of 100,000-300,000 Scoville Units in the natural state and which, as utilized in the preferred embodiment, is highly concentrated to produce a pungency rating of from 1,000,000-1,500,000 Scoville Units. To overcome the incompatibility problem with mixing oleoresin with marine coatings, the present process mixes the capsaicin (alkaloid) with a selected solvent and with silicon dioxide to form an improved additive which is more compatible with the coating material and with coloring agents, pigments, and dyes.
Compatibility of the present additive with the coating mixture is also improved by adding a binding agent to the coating material, prior to adding the previously described additive. The present invention also discloses a process for producing capsaicin crystals which prevents, to a large degree, the "bleedout" of the anti-foulant capsaicin into the coating mixture and permits greater loading of the coating with the capsaicin than the process using a liquid oleoresin capsaicin mixture. Mixing the crystalized capsaicin with various coating materials, such as marine paints, or epoxy or polyurethane compounds, reduces the adverse effects on the curing time and physical properties of the coating material which might otherwise occur when using a liquid oleoresin capsaicin.
A much longer lasting and durable anti-fouling coating is obtained by combining the present additive with finely divided abrasion resistant particles (ceramic). The improved compatibility of the present additive with other materials also makes it suitable for use in molding products and creating articles of manufacture having a surface with the capsaicin contained therein.
The present invention is distinguished over the prior art in general, and these patents in particular by an anti-fouling coating which utilizes capsaicin as an anti-fouling agent. In a preferred embodiment, finely divided capsaicin, an oleoresin capsaicin liquid solution, or crystalized capsaicin is mixed with a suitable corrosion resistant epoxy resin which is then mixed with a hardening catalyst and applied to the surface to be treated. In some applications, finely divided inert particles may be added to impart additional desirable characteristic to the surface. The capsaicin constituent used in the coating preferably has a rating of from about 100,000 to about 1,500,000 Scoville Heat Units. The capsaicin may be mixed with a silicon dioxide and then solubilized into a free-flowing homogeneous liquid oleoresin composition by adding a solvent to increase solubility and facilitate mixing. The capsaicin may also be formed into crystals which are mixed with the coating material. The anti-fouling composition can be used in combination with conventional anti-fouling coatings and paints and binders and applied to wood, metal, and plastic surfaces. The anti-fouling composition may also be added to other materials in molding processes to form various articles of manufacture and molded products, such as boat hulls and water pipes, which resist fouling by organisms common in fresh water and sea water.